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But the atmosphere of the Crypt begins to feel close-and the walls, we fear, are damp; let us, therefore, adjourn again to the

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GREEN-ROOM.

STRANGE," exclaimed the philosophical Macready, "that distance of space should be distinguished by changes that had failed to mark the course of time." Yes," we replied, breaking in upon the discourse, "the late Mr. Taylor, of Norwich, says of Kotzebue, that having succeeded on every European stage, his power over Space already transcended that of Shakspere; it remained to be seen, whether his power over Time will stand the test of centuries.'

"The reputation of Madame is more like that of Shakspere than that of Kotzebue. From the year 1797 to the present, her celebrity in England has suffered no abatement. But in Scotland and America she has not been able to assume a position. It were, truly, a curious speculation to estimate the different values of Fame in Duration and Fame in Extension."

"Why," said common-place Bunn, "the Americans had not seen her as we had in the gaiety and loveliness of youth-what she is, therefore, derived no prestige from what she was."

There it is," said we.

"The fame in space is constituted of sensationsthat of time is an affair of the intellect. The acting of Vestris now, makes a demand upon the understanding. Moreover, we have to imagine the beauty and the juvenility that we no longer witness. The English public will, whatever may be said to the contrary, look through the visage into the mind,—a faculty not to be yet expected from the Americans; least of all if they happen to be, as it seems they were, in a state of disappointed expectation."

"So much," said Vandenhoff, "depends, in all these affairs, on circumstances. The accident of being rejected in America, only increased the warmth of her reception on her return to England."

How much longer this conversation might have continued we know not; but Mr. and Mrs. Charles Matthews entering, made the topic one of considerable delicacy; it was, therefore, very properly dropped.

Our attention continues to be fixed on COVENT GARDEN THEATRE, as the only place where the National Drama is presented on an extensive and ambitious scale. All the good actors there-Macready, Vandenhoff, Phelps, Ward, Elton, Serle, Anderson; Mrs. Warner, and Miss Faucit. At this period of the year, however, when inexplicable dumb-show, in the shape of Pantomime, usurps the throne of Melpomene and Thalia, we have little opportunity for remark. We are, however, happy to hear, that two tragedies have the chance of appearing. There is much promise about the one last read*; and David Rizzio is by a man of talent, and, in its amended form, will prove

attractive.

The exertions of Mr. Macready have evidently succeeded in forming the public taste to a better point than it had previously attained. It ought to be the task of critics, daily, weekly, and monthly, to urge public opinion to a demand of yet higher excellence, not rejecting, however, the actual for the ideal -the present attainment for some future possibility. What Mr. Macready has been doing, will force a future manager to attempt the highest standard of dramatic production. The time will come when the public mind will require, not only the mise au scène in as great, or greater, perfection than it can be given in Paris, but something more than the utmost theatrical display can achieve. All the possibilities of Poetry must be embodied in those attractive shapes which only the stage can realise. The New Spirit of an æra, as original in genial art as that of the Elizabethan age, must receive the warmest welcome and readiest assistance that the theatre can render. The present state of public developement has called the First of modern Actors to the helm-the next evolution will require the First of modern Poets, whoever he may be. The beau ideal of a management never can be reached until that consummation shall have been effected.

Richelieu; or, the Proud Brother; by Sir Edward Lytton Bulwer, Bart.

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No. 1.-THE UNDULATORY THEORY OF LIGHT. BY CHARLES TOOGOOD DOWNING, M.R.C.S.-Author of the " Fanqui in China," &c.

Ir may be remembered, that at the last meeting of the British Association at Newcastle, after Sir David Brewster had read a most interesting paper on the combined action of grooved metallic and transparent surfaces upon light, there was a dead pause throughout the assembly. After a while, Sir John Herschel said, that the members must not suppose that the silence which prevailed betokened apathy respecting these splendid researches of

Sir David Brewster, but that it arose from the extreme difficulty of following with sufficient rapidity for discussion such an absolute torrent of new matter: silence was to be attributed to the general feeling, that the subject was too vast to be at once grasped by any one. Indeed the discoveries of Sir David Brewster, whether viewed in relation to the intervals at which they succeeded each other or the instruction they conveyed, equally filled the auditors with delight and astonishment. At another time, after hearing read an account of a new kind of polarity in homogeneous light, the same great astronomer, Sir John Herschel, remarked, that in whatever point of view light was considered, or in whatever field of experiments respecting it we became engaged, we were sure to meet with something to interest us by its novelty, or to astonish us by the unsuspected nature of the result: for his own part, his long absence from home had placed him very much in arrear of the present state of the Science.

If, then, so great a philosopher acknowledges his deficiency, and the scientific collected from all parts are dumb with astonishment at the wonderful march of discovery, it may be expected that the general reader will at least be equally perplexed. The fact is, that so many new phenomena have lately been discovered in this branch of science, that it is impossible for any one to keep pace with them, unless he devotes himself almost entirely to that particular study. In order, however, to obtain a proper share of information, and to be enabled to appreciate the importance of what is taking place, it is necessary to go back to the fundamental principles on which all these after-strata are founded. As no one subject, at the present time, occupies more of the attention of the learned than light and optics, and as frequent allusions are made to the undulatory theory, we thought it as well to introduce a short and familiar account of its origin and progress. More especially as, at this very moment, there is an animated discussion taking place on the subject, between two of the greatest men in science that Great Britain can boast.

In the investigation of nature, in the endeavour to dive into and explain the secret mysteries of her operations, it has frequently been remarked, that those things which more particularly elude the grasp of the mind of man, and defy his attempts, are those which are constantly obtruding themselves upon his notice. They stimulate his curiosity by frequent appeals to his senses, and thus awaken his industry to the search; while at the same time, by their intangibility and etherialism, they almost deny a possibility of success. The laws and properties of light have been studied with untiring perseverance by the greatest mathematicians and astrologers, and among those who have rendered themselves famous by their discoveries, may be mentioned the names of Snellius, Descartes, Huygens, Newton, Hooke, Euler, Malus, Young, Fresnal, Fraunhofer, Herschel, and Brewster. The success which has attended these labours, especially of late years, has been completely dazzling. Phenomenon after phenomenon has arisen in quick succession, and been applied with such profound skill to the elucidation of subjects

heretofore considered beyond the reach of man, that we are equally lost in amazement and admiration.

Light is arrested by some bodies, while it passes freely through others; is reflected from polished surfaces; is bent or deflected from a rectilinear course in passing near various bodies; is capable of dispersion and condensation in passing through certain media; it has a chemical action on certain compounds; and it apparently enters into the composition of substances, and is again extracted from them at pleasure. It is also well known to travel at the rate of 192,000 miles in a second of time: a velocity so greatly exceeding any motion produced by the art of man, that it almost defies the power of imagination.

Matter of such extreme tenuity, and at the same time possessed of such wonderful properties, may be well supposed to have excited endeavours to discover its nature. In fact, suppositions or theories of light, and its action on the eye to produce the phenomena of vision have been handed down to us from very remote ages. The Pythagoreans believed that it consisted of particles emanating from the sun and other luminous bodies, and entering the pupil of the eye; while Aristotle regarded it as a mere quality of matter. Plato and his followers considered that vision was occasioned by particles of something emanating from the eye, and feeling, as it were with a hand, the surfaces of objects. They were puzzled, notwithstanding, with the fact of this power being available only in the presence of a luminous substance, and could not explain why an object should not be equally well seen in the dark. Since those times, a variety of speculations have been offered, many of them of great ingenuity, and capable of explaining some of the more simple phenomena of optics, but totally defective when more scrupulously examined.

Two theories have of late years engaged the attention of philosophers. The first is the Newtonian, or corpuscular doctrine, which supposes light to consist of excessively minute molecules, or particles of matter, projected from the sun and other luminous bodies in every direction, with the immense velocity due to light, and acted on by attractive and repulsive forces residing in the bodies on which they impinge; by which means they are reflected, refracted, and otherwise turned from their rectilinear course, according to the laws observed. This theory, which was the one adopted by the great philosopher whose name it bears, explained in a satisfactory manner the laws of reflection, refraction, and the dispersion of light, but has been almost entirely neglected on account of the more ready and satisfactory explanation of recent discoveries. afforded by the other hypothesis. One grand objection has been urged against the corpuscular theory which would appear, prima facie, conclusive. If light consisted of particles of matter, even if we suppose them to be many thousand times smaller than a grain of sand, yet, propelled at the astonishing rapidity before mentioned, the momentum they would acquire in reaching the earth from the sun, would be sufficient to overturn and destroy every thing they struck. Yet it is found that the strongest light does not disperse the finest particle of dust, or produce any perceptible effect upon

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instruments especially constructed for the purpose of detecting its impetus. If, also, matter was continually emanating from the sun through successive ages, how is it that the substance of that luminary has not greatly decreased?

These, and other reasons equally cogent, inclined philosophers to seek some other explanation of the mysteries of light; and hence arose the Huygenian, or undulatory theory. Huygens or, as he is called, Huygenius, a Dutch mathematician of profound knowledge and acquirements, first communicated his notions to the Academy of Sciences at Paris in 1678, and subsequently published them, with enlargements, under the title of " Traité de la Lumière." In the undulatory theory, it is supposed that an excessively rare, subtle, and elastic medium, or ether, as it is called, pervades the universe; that it fills all space, permeating all material bodies, and occupying the intervals between their molecules; that it is inappreciable when at rest, and, either by passing freely among them, or by its extreme tenuity, does not interfere with the motions of the earth, the planets, or the comets, in their orbits, as far as can be ascertained by the most delicate astronomical instruments; and that it has inertia, but not gravity. The molecules of this ether are susceptible of being set in motion by the agitation of the particles of ponderable matter; and when any one is thus set in motion, it communicates a similar motion to those adjacent to it, and thus the motion is propagated farther and farther in all directions, according to the same mechanical laws which regulate the propagation of undulations in other elastic media, according to their several constitutions, as air, water, solids, &c.

In the interior of refracting media, such as glass or water, the ether still exists, but, on account of the attraction of matter, in a state of less elasticity, compared with its density, than when in vacuo, and therefore the elasticity of the ether in the interior of media is less, relatively speaking, in proportion to their refractive powers. Wherefore it follows, that vibrations communicated to the ether in free space are propagated through refractive media, by means of the ether in their interior, but with a velocity corresponding to its inferior degree of elasticity. The sensation of light is produced when regular vibratory motions of a proper kind are propagated through the ether, and, by passing through our eyes, reach and agitate the retina, thus bearing a more or less close analogy to the way in which our auditory nerves are affected with the sensation of sound by the vibrations of the air. The colour and brightness of light are explained by a similar analogy. For, according to the theory of sound, the frequency of the aerial pulses, or the number of excursions to and fro from its point of rest made by each molecule of the air, determines the pitch, or note; so, in this theory of light, the frequency of the pulses, or number of impulses, made on our nerves in a given time by the etherial molecules next in contact with them, determines the colour of the light; and that, as the extent of the motion to and fro of the particles of air determine the loudness of the sound, so the amplitude, or extent, of the excursions of the etherial molecules from their points of rest, determine the brightness or intensity of the light.

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